Playing with Fire

I haven’t mentioned it here before, but my other half took up Ceramics a few years ago, doing a Certificate IV at the local TAFE in Noosa. She’s so good at it, Glenda never ceases to amaze me…..

In 2010, she won the Student Travelling Scholarship to improve her skills; the basis of her submission, apart from the extraordinary pots she made for the competition, was sustainability. The craft/art of pottery I now realise takes humungous amounts of energy to fire the work. Because Glenda usually uses the TAFE college’s kilns to fire her work, we are not aware of the cost of a firing, it’s included in her fees. But the other day we used someone else’s kiln in a desperate effort to finish the work she was preparing for her current (and small) exhibition in Gympie. Ian said it would cost $15 in electricity. Which to me proves how cheap electricity still is. Doing the sums, that’s around 70 kWh of electrical energy, what we use here in ONE MONTH! Now you know why she’s looking at avenues for doing this less unsustainably….

When Glenda prepared her submission for the scholarship, she started looking for other practitioners of “sustainable pottery”…… and only found one. His name is Steve Harrison. Occasionally, one is lucky to meet someone truly extraordinary. Steve is one such person. Unlike me, he is a perfectionist, and everything he turns his hand to is exquisite….. from the extension he built onto the old school where he and his wife Janine live, to the work he creates, often from scratch as he makes his own glazes, and even porcelain. He only uses local materials, and is dead keen on wood firing, as he believes, like me, that fossil fuels are over used and climate tipping points are probably with us already.

Steve had 3 kW of PV installed years before it became a fad, and the whole studio is made of mud bricks. They too also cook on a wood stove! Read all about it here, just click on the sustainability tab of his website. In fact, click everything ….. you will find it all fascinating. Glenda was so excited to find these two, I remember her telling me “they drive slowly like you do to save petrol!”

To cut to the chase, Glenda and I spent three days with Steve and his wife, soaking up all the stuff we had to learn, not least me who knew almost nothing about ceramics. Steve makes his money not from Pottery so much as building kilns….. his favourite is the Bourry Box (invented by a Frenchman) which is a large brick structure capable of firing large pieces, or lots of small ones. We are certainly not at this stage yet, though I’m really keen to build one one day, especially if we do make it to Tassie where firewood is abundant. It was also the visit to Tassie following on from Steve’s studio that convinced me we had to move. Glenda went to a wood firing convention in Deloraine, the whole island is teeming with like minded people!

Steve introduced me to the pedal bin kiln…. I could not believe that it was possible to do this stuff in a rubbish bin…! The $300 kiln. Now that’s right up my alley…!

I found a never used stainless steel Freedom Furniture 50L pedal bin on eBay someone didn’t want for half its brand new price, gutted it, and installed special ceramic fibre insulation inside it with ceramic “buttons” Glenda made at TAFE and special nickel wire that won’t melt at well over 1000 degrees. I bought a 1200mm long piece of 100mm stainless steel flue from the local BBQ Galore store, cut and drilled all the appropriate holes, and presto (well it took me a year actually… no one procrastinates as well as me!) we had a kiln. The dearest part was the pyrometer which has to be connected to a multimeter to gauge temperature. More about this later…..

Conventional firings take hours and hours, which is why kilns use so much energy (kiloWatts x hours = kiloWatthours – kWh) but what we did here is a Japanese technique called RAKU, which involves quickly heating the pottery to about 1100°C, and then rapidly smothering the artwork in sawdust. Here’s a quick demo…

My kiln’s a lot smaller than that one, one has to start somewhere…

This is shortly after starting the fire. The flue is just starting to discolour (the bin did not at all, so effective is the insulation). The pyrometer is the bit sticking out the side, which you can see is connected to my multimeter

In this close up, the fire is building up. You can clearly see the insulation at the right hand side of the aperture where I insert the wood. The two bolts support a fire brick which Glenda’s work is sitting on. Also visible are two of the “staples” I made of that special nickel wire to hold the insulation against the bin wall.

The pyrometer is a thermocouple; that is, two wires of dissimilar metals welded at the end exposed to the heat, which generates an electric current, measured in milliVolts. Attach a multimeter to it, and you can convert the voltage to degrees C. Theoretically! I downloaded a conversion table, but it soon became clear that the table in my laptop had no similarity whatsoever with the readings my meter was giving me…! At 1000°C, the voltage was supposed to be 4.8mV, but my meter was soon reading well over 10, and by the time the glazing melted (by visually looking inside the kiln!) it read 36mV…… so it’s back to the drawing board with that one, I need another chart…

The amazing thing is how it only took about one kilo of wood to get the kiln to over 1000°C…… that’s under 3 kilo of CO2 emissions.

Regardless of flying blind with the temperature, Glenda was ecstatic with the results which we reduced in an old stainless sink with spectacular flames as the sawdust caught alight.

It’s all hanging in the gallery in Gympie now, we’re both exhausted, but Glenda’s thrilled to bits, what more could you ask?

2 responses

20072013

Brian Charlton. Carina Hts. Brisbane.(16:38:29) :

I believe your eventual departure from the Sunny Coast to Tasmania will be
a substantial loss to Queensland. I just hope you continue with your articles
which I find are riveting and essential reading. I trust your wife’s exhibition in
Gympie is a raging success. Keep up your good work.